The present invention relates to a microwave oven including a digital control system and a heater means for performing electric cooking or browning operation.
The present invention relates, more specifically, to a cooling fan system of a microwave oven including a digital control system and a heater means disposed in the oven cavity.
Recently, a digitalized microwave oven has been developed, which includes a digital control system comprising a semiconductor microprocessor for controlling microwave generation, and a keyboard panel for introducing desired program commands into the semiconductor microprocessor. A typical microwave oven of the above feature is commercially available as "Microwave Oven R-9000" manufactured by SHARP KABUSHIKI KAISHA. A typical control system is disclosed in U.S. Pat. No. 4,011,428 entitled "MICROWAVE OVEN TIMER AND CONTROL CIRCUIT" issued on Mar. 8, 1977. Another typical control circuit is described in copending application, "MICROWAVE OVEN WITH A PROGRAMMABLE DIGITAL CONTROL CIRCUIT," Ser. No. 792,222, filed on Apr. 29, 1977 by Tsuneo Kawabata, Minoru Makita, and Sigeaki Masuzawa, and assigned to the same assignee as the present application.
On the other hand, a microwave oven including a heater means for performing electric cooking or browning operation has been developed. A typical microwave oven including a browner unit is disclosed in U.S. Pat. No. 3,878,350 entitled "MICROWAVE COOKING APPARATUS" issued on Apr. 15, 1975. An example of a combination microwave oven and an electric heating oven including a heater means for performing electric heating cooking is described in copending application, "MICROWAVE OVEN WITH A CAPABILITY OF FUNCTIONING AS AN ELECTRIC HEATING OVEN," Ser. No. 776,358, filed on Mar. 10, 1977 by Yutaka Takagi and Munemitsu Toyoda, and assigned to the same assignee as the present application.
Accordingly, when the digital control system is adapted to a microwave oven including a heater means, programmed cooking inclusive of the microwave cooking and electric heating cooking can be conducted. However, attention should be directed to the fact that the exterior of the oven cavity is also heated up in the electric heating cooking operation. The semiconductor microprocessor included in the digital control system must be protected from a high temperature.
Accordingly, an object of the present invention is to provide a microwave oven including a digital control system and a heater means.
Another object of the present invention is to project a digital control circuit from a high temperature in a combination microwave oven and electric oven.
Still another object of the present invention is to provide a novel cooling system for a combination microwave oven and electric oven.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a combination microwave oven and electric oven is provided with a digital control circuit comprising a semiconductor microprocessor. The semiconductor microprocessor controls the programmed microwave cooking and electric cooking. The semiconductor microprocessor is mounted on a circuit board which is secured to a rear surface of a control panel including a plurality of instruction keys for introducing desired program commands into the semiconductor microprocessor.
A cooling fan system is provided for cooling a microwave generation means and the semiconductor microprocessor during the microwave cooking operation and the electric heating operation. A control system functions to activate the cooling fan system for a predetermined period of time after completion of the electric heating operation, thereby preventing occurrence of a high temperature around the semiconductor microprocessor.